1. Field of Invention
The present invention relates to a portable monitoring device to monitor the internal electrical impulses generated by a live mammal, including humans, and in particular to monitor and produce EKG's and EEG's with a small pocket-size device.
2. Prior Art
Numerous portable electronic devices designed for processing electrical signals from the heart are described in the patent literature. There are many problems with these devices as they are described. All of the devices except for the cathode ray tube device, give as output a flashing light, an audio tone, or a meter deflection. There is no way of knowing whether the light, tone, or meter deflection represents electrical activity or noise.
Anyone familiar with EKG's knows that intermittent lead contact is a problem even with adhesive electrodes, and any device which has to reliably record or detect biopotentials has to have the capability of informing the operator when a lead failure has occurred. High impedance amplifiers as described in some of the patents are helpful, but good contact is still a problem. In conventional EKG's and EEG's poor lead contact is usually obvious by the characteristic noise pattern on the recorded signal. For devices with only a light, audio signal, or meter the cadence is supposed to indicate proper or improper operation; however, the signal and the noise spectrum can be sufficiently close that the device can be "fooled" into indicating a valid signal when indeed none exists. The device can also misinterpret lack of contact as no signal being sent. These lead failure modes can and do occur without any obvious misapplication of the device or electrode.
The cathode ray tube device is too bulky to be accepted as an easily portable device for use in field or on site situations. For example, the device described in U.S. Pat. No. 3,776,228 to Semler (issued 12/73) has a minimum electrode spacing of 7 cm. It also has a fluid reservoir present. This fluid is undesirable because of its bulk and its potential for leaking over both the internal parts of the device, and the person carrying the device. The fluid could also become contaminated with microorganisms that could spread disease from patient to patient. It is common practice to use a sterile interface between the patient and the measuring device (i.e., disposable electrodes). This device describes the electrodes as being made out of "highly conductive material such as silver or nickel." These kinds of electrodes are highly subject to polarization potentials, which are manifested as noise currents. A much better kind of electrode is one made out of a combination of silver with silver chloride, which has much less polarization.
It is naive to propose that physicians and paramedics are going to spend an adequate amount of time to learn the characteristic: "beeps" of the device described in U.S. Pat. No. 3,830,227 to Green (issued 8/74). In fact, no data is presented to show that any such characteristic beeps occur. There are many different patterns on the EKG that are clinically distinct, but show up as only very subtle changes on the EKG record. Also, since the currently accepted method for determining the electrical activity of the heart consists of interpreting EKG records, it is very doubtful that the devices described would be accepted by the medical community.
The device described in U.S. Pat. No. 3,991,747 to Stanley et al (issued 11/76) requires supplemental processing equipment to be of value. Its other considerations are as noted above.
U.S. Pat. No. 4,350,164 issued Sept., 1982 to Dr. Joseph L. Allain, one of the co-inventors hereof, is noted. Even the Allain device of the '164 patent, although a great advance over the prior art, was capable of improvement, both in its over-all range of its capabilities and in some of the mechanical details of its housing, linkages and connections of its preferred embodiments.
Another very important requirement of a life detection monitor is its ability to store an EKG or EEG waveform. If a patient has other than an obvious condition, which is often the case, it is necessary for the physician or paramedic to spend a few minutes analyzing the same strip of data. This is not possible to do with the current devices as they are described.
For medicolegal purposes it is desirable for the device to be able to store a portion of the waveform for later read-out on a permanent record. This situation would occur if a patient were pronounced dead at the scene of an accident, or after a heart attack. Unless the telemetry equipment were immediately available, this would not be possible with the current, prior art devices.
Thus important considerations partially or completely missing in the totally portable life detection devices as described in the prior art are as follows:
(1) Noise considerations; PA0 (2) Validation of the method; PA0 (3) Brain wave detection; PA0 (4) Stored waveform modes; PA0 (5) Freeze modes; and/or PA0 (6) Small electrode spacing.
3. Summary Discussion of the Present Invention
Numerous advancements in the state of the art have been incorporated in the life detection monitor of the present invention.
These advancements include those in the circuitry, medical features, storage of data, packaging and improved design of the supplemental swing down or out electrodes.
It is thus a primary object of the present invention to provide life detection (e.g. EKG/EEG) portable, pocket-size monitor that is highly reliable in its operation and of compact, pocket-size packaging.
It is a further object to provide such a monitor with many different features and capabilities, including for example data storage as well as preferrably both EEG and EKG capabilities.
It is another object to provide the supplemental, swing out electrodes for enhanced spacing in an improved way.
It is a final, general object to cure the problems detailed above with respect to the prior art.